title: Ca3N2 and Mg3N2: unpredicted high-pressure behavior of binary nitrides.
abstract: High-pressure synthesis allows both fundamental and materials science research to gain unprecedented insight into the inner nature of materials properties at extreme environment conditions. Here, we report on the high-pressure synthesis and characterization of γ-Ca(3)N(2) and the high-pressure behavior of Mg(3)N(2). Investigation of M(3)N(2) (M = Ca, Mg) at high-pressure has been quite challenging due to the high reactivity of these compounds. Ex situ experiments have been performed using a multianvil press at pressures from 8 to 18 GPa (1000-1200 °C). Additional in situ experiments from 0 to 6 GPa (at RT) at the multianvil press MAX 80 (HASYLAB, Beamline F.2.1, Hamburg) have been carried out. The new cubic high-pressure phase γ-Ca(3)N(2) with anti-Th(3)P(4) defect structure exhibits a significant increase in coordination numbers compared to α-Ca(3)N(2). Contrary, Mg(3)N(2) shows decomposition starting at surprisingly low pressures, thereby acting as a precursor for Mg nanoparticle formation with bcc structure. Soft X-ray spectroscopy in conjunction with first principles DFT calculations have been used to explore the electronic structure and show that γ-Ca(3)N(2) is a semiconductor with inherent nitrogen vacancies.
authors.affiliation: Ludwig-Maximilians-Universität München, Department Chemie, Butenandtstrasse 5-13, D-81377 München, Germany.
authors.forename: Cordula
authors.initials: C
authors.lastname: Braun
authors.forename: Saskia L
authors.initials: SL
authors.lastname: Börger
authors.forename: Teak D
authors.initials: TD
authors.lastname: Boyko
authors.forename: Gerhard
authors.initials: G
authors.lastname: Miehe
authors.forename: Helmut
authors.initials: H
authors.lastname: Ehrenberg
authors.forename: Peter
authors.initials: P
authors.lastname: Höhn
authors.forename: Alexander
authors.initials: A
authors.lastname: Moewes
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schnick